deficient

American  

[dih-fish-uhnt] / dɪˈfɪʃ ənt /

adjective

1. lacking some element or characteristic; defective.

   deficient in taste.

2. insufficient; inadequate.

   deficient knowledge.

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noun

1. a person who is deficient, especially one who is mentally defective.

deficient British  

/ dɪˈfɪʃənt /

adjective

1. lacking some essential; incomplete; defective

2. inadequate in quantity or supply; insufficient

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Other Word Forms

• deficiently adverb
• nondeficient adjective
• nondeficiently adverb
• predeficient adjective
• predeficiently adverb
• undeficient adjective
• undeficiently adverb

Etymology

Origin of deficient

First recorded in 1575–85; from Latin dēficient-, stem of dēficiēns “failing,” present participle of dēficere “to fail, run short, lack, weaken,” from dē- de- + ficere, combining form of facere “to do, make” ( do ¹ )

Explanation

Deficient means not enough or not adequate. Maybe you were deficient in caffeine that day. Maybe you were lacking in study time. But no doubt about it: you came up with a deficient number of correct answers on the physics test. If your new car fund remains deficient, you don't have enough money to buy a new car. This presents a problem if your current car is deficient in some way — say, it no longer has enough engine power to drive up a hill. You may not feel you have what it takes to get a job, but the reality is you will have to choose between indulging your own deficiencies in this area or the car's.

Example Sentences

A panel of medical experts, asked by prosecutors to investigate Maradona's medical team, said the treatment he received at his home was "deficient and reckless".

From BBC • Apr. 14, 2026

These provide calories but lack the sterols bees need, leaving colonies nutritionally deficient.

From Science Daily • Mar. 27, 2026

The agreement Barnett reached with LaBeouf “contained a deficient and unlawful NDA that is unenforceable,” under California’s Stand Together Against Non-Disclosure Act, according to the complaint.

From Los Angeles Times • Mar. 26, 2026

Iran, which is an IMO member but does not sit on its council, hit out at the declaration, branding it "one-sided, unfair, inaccurate and legally deficient".

From Barron's • Mar. 19, 2026

Both Call and the Captain seemed to regard me as mentally deficient, since I couldn’t appreciate their marvelous humor.

From "Jacob Have I Loved" by Katherine Paterson

Related Words

• defective
• faulty
• flawed
• impaired
• incomplete
• inferior
• insufficient
• lacking
• scarce
• skimpy
• unsatisfactory
• weak